The short answer: a genogram symbol is not meaningful by shape alone. It makes a claim in one of four layers—who a person is in the diagram, how people are structurally connected, what condition or event is recorded, or how a relationship was described. Read those layers separately, and require a dated legend for any mark that is not unmistakable in the chosen notation.
That rule prevents the most common error: treating a line or fill as a diagnosis. A zigzag relationship line can record that an informant described conflict; it does not prove abuse, identify a cause, or say the relationship is always conflictual. A filled person symbol can mean “affected by the condition named in this legend”; it does not mean “generally ill.”
Scope and last review: reviewed August 20, 2026. This guide explains how to read and review a genogram; it is not a diagnostic instrument or a substitute for an organization’s clinical, genetics, privacy, or recordkeeping policy.
First decide whether you are reading a genogram or a pedigree
A genogram maps a family system. It may combine family structure with health, life events, household membership, and reported relationship patterns. The U.S. Substance Abuse and Mental Health Services Administration describes it as more than a family tree and shows structural, condition, and interaction symbols in its 2020 family-therapy guidance.
A pedigree is narrower: it maps family relationships and the inheritance of a specified trait or health condition. The National Human Genome Research Institute’s glossary, updated August 20, 2026, uses that inheritance-focused definition. Clinical genetics also has a maintained pedigree nomenclature: the National Society of Genetic Counselors’ 2008 review found it was the only consistently acknowledged standard for family-health-history pedigrees, and a 2022 focused revision clarified sex and gender representation.
The two diagram families overlap, but their marks are not automatically interchangeable. A double line, for example, may be used for emotional closeness in a therapy genogram while paired relationship lines have a different, specific meaning in pedigree notation. The title, purpose, legend, and governing convention must resolve that ambiguity.
The four claim layers
| Layer | What it may record | What it does not establish by itself |
|---|---|---|
| Person | A person, index person, age, dates, identity, or role | Diagnosis, legal status, or self-described identity unless labeled |
| Structure | Partnership, separation, parentage, sibling order, adoption, fostering, or household boundary | Emotional quality or current legal status unless the convention says so |
| Condition or event | Death, a named condition, substance use, pregnancy event, or another dated fact | Cause, severity, certainty, or clinical confirmation unless annotated |
| Relationship quality | Reported closeness, distance, conflict, cutoff, or another defined pattern | Who caused the pattern, whether it is mutual, or whether it persists over time |
Keep the layers visually distinct. Structure should remain readable when condition fills and relationship overlays are removed. If the drawing becomes impossible to follow without color, the encoding is too fragile for printing, photocopying, or accessible review.
What the most common marks can safely mean
The table below gives a review rule, not a universal symbol catalog. Project and discipline conventions still control.
| Mark | Safe reading | Required check |
|---|---|---|
| Circle, square, or diamond | A person node under the sheet’s stated convention | Do not infer gender identity or sex assigned at birth from geometry alone; follow the current practice convention and labels |
| Diagonal slash through a person | The person is deceased | Add a date or age when known; the slash does not state cause of death |
| Filled or partly filled person | The person is affected by the condition keyed to that fill | Name every fill or pattern in the legend; separate reported history from confirmed diagnosis |
| Horizontal partner line | A partnership or union defined by the notation | Annotate marriage, cohabitation, separation, divorce, and dates instead of guessing from one generic line |
| Vertical descent line | A parent–child connection defined by the notation | Use the applicable adoption, foster, donor, or gestational convention when biological descent is not the intended claim |
| Parallel relationship line | Often “close” in therapy-oriented legends | Check the legend: similar line patterns can mean something else in pedigree notation |
| Zigzag relationship line | Often a reported conflict pattern | Record source and date; do not silently upgrade “conflict” into violence or abuse |
| Boundary around several people | A household or other explicitly named grouping | State the date because household composition changes |
The 2022 NSGC practice resource matters here. It did not solve inclusion by inventing a new geometric symbol for every identity. It clarified how pedigree users should distinguish sex assigned at birth from gender and use respectful, clinically meaningful language. For a mixed clinical audience, a label and legend are safer than assuming every reader learned the same circle-and-square rule.
Worked example: read one mark at a time
Suppose a three-generation sheet shows Maya as the index person, her mother Lena with a filled symbol, a slash through her deceased grandfather Omar, and a zigzag line between Maya and her father.
Read it in four passes:
- Person: the index marker identifies Maya as the focus of this drawing. It does not make her “the patient” unless the document says so.
- Structure: the connection lines show the family links asserted by the sheet. Check adoption, stepfamily, donor, and household annotations before assuming biological parentage or co-residence.
- Condition: Lena’s fill means only the condition named in the legend. If the legend says “type 2 diabetes—family reported,” do not rewrite it as a verified diagnosis.
- Relationship: the zigzag means the defined conflict category, as reported for the date and informant stated. It does not establish blame, frequency, or risk.
That procedure turns the diagram into reviewable documentation. Without the legend, source, and date, the same drawing invites four different kinds of overclaiming.
A five-step review before sharing the sheet
- Name the job. Is this for family-therapy assessment, genetic counseling, education, case formulation, or a personal family map? The job determines the convention.
- Print the legend on the page. Define shapes, fills, line styles, abbreviations, colors, and any project-specific symbols.
- Attach provenance. Record who prepared the diagram, the date, the informant or record source, and whether each sensitive item is reported, observed, or clinically confirmed.
- Minimize sensitive data. Include only information necessary for the stated purpose. A genogram can expose information about relatives who are not the client.
- Test a grayscale copy. Labels, patterns, and line styles should preserve meaning without color, hover text, or access to the original software.
Common failure modes
- Mixing conventions: pedigree symbols, family-therapy relationship lines, and custom software icons appear together without a legend.
- Turning absence into fact: a blank condition mark is read as “unaffected” when it may only mean “not assessed.”
- Freezing a relationship in time: “conflict” is recorded with no date, source, direction, or context.
- Encoding too much: diagnoses, identities, events, relationships, and household boundaries compete on one crowded node.
- Treating the diagram as evidence: a clean graphic can make second-hand or uncertain information look verified.
- Using color as the only channel: the meaning disappears in print or for a reader with color-vision differences.
The practical next step
Before drawing, write a one-page specification: purpose, notation family, generations in scope, person fields, structure rules, condition legend, relationship categories, source labels, privacy boundary, and review date. Then use ChatDiagram’s genogram maker to draft the structure and add only the annotations that the specification permits.
End the review with one question for every mark: What exactly is this claiming, who supplied that information, and where is the legend that lets the next reader reach the same interpretation?